The present invention relates to A-frame for supporting objects, such as glass sheets or other sheet materials, during transport and storage. More particularly, the present invention relates to a foldable, stackable, transportable, A-frame rack with a low center of gravity and improved load securing assembly for storing and transporting materials, such as glass sheets or other sheet materials.
A-frame structures have long been used to support sheet materials standing on edge. Sheet materials may include construction materials, such as plywood, plaster board or paneling, as well as sheets of glass.
Glass panes, in particular, may be stored in this fashion. Glass is often made in large sheets which are heavy and breakable. Because of glass""s weight and breakability, stability and protection of the sheet material while in storage and transit are especially important.
Various techniques are commonly employed for the storage and shipping of glass sheets. Harp or slot racks, for example, may be employed to store individual sheets of material, such as glass. A slot rack consists of a series of vertical partitions between which sheets of glass may be placed on edge for convenient storage. A harp rack is similar to a slot rack except that it employs tensioned vertical cables or wires to separate the individual sheets of material, such as glass. Harp or slot racks are convenient for storing small quantities of glass but require individual handling of each sheet and are not particularly appropriate for transporting glass to another location. Furthermore, these types of racks are not readily adaptable to automated transport devices for moving sheets of material from one location to another.
A further option for the transport and storage of objects, such as sheet of glass or other sheet materials, is the use of A-frame racks. An A-frame rack generally includes two or more A-frames, which take the form of a tall, often truncated, isosceles triangle. The A-frame rack further includes a support at the base upon which glass sheets may be stood on edge and then leaned against the A-frame rack for support. A-frame racks are convenient for stationary storage purposes because once the sheets of glass are in place, they are held by gravity and well protected from falling. Straps or other securing mechanisms are used to hold glass panes when A-frame racks are transported
In the float glass manufacturing process, molten glass is commonly floated in long ribbons, which are cooled and then cut to size and stored until they are ready for the next step in a manufacturing process or for shipping. The cut sheets of glass are commonly loaded one at a time onto one side of an A-frame rack. When one side of the rack is full, the rack is pivoted through 180 degrees to make available the second side for loading. While the second side is loading, the glass on the first side is packaged as desired and moved by means of a crane onto a support for storage until needed.
Thereafter, the glass is unloaded from the A-frame support and loaded onto a truck or other delivery transport, using one of several transportable glass supports, as, for example, another A-frame support. At the delivery location (for example, a manufacturing line for applying a coating to the glass), the glass is again unloaded and positioned so as to be used. The resulting glass is then again loaded onto a support and is moved to, for example, a station where the glass panes are converted into insulating glass (xe2x80x9cIGxe2x80x9d) units, the glass again being unloaded and reloaded. Finally, the IG units are transported to a plant where they are unloaded and converted into framed windows. Thus, the glass may be repeatedly loaded and unloaded, leading to substantial expense and risk of damage.
A variety of A-frame rack designs already exist that are intended for use in the storage of glass as well as the shipping of glass sheets. When used for shipping, it is common for A-frame racks to be fashioned as reusable structures that are shipped loaded with glass sheets and returned empty. In an effort to minimize shipping costs on the return trip, certain A-frame configurations have been proposed that are intended to be disassembled or collapsed when empty to minimize shipping bulk.
For example, U.S. Pat. No. 3,878,942 issued to Hansen et al., discloses an A-frame structure that is secured to the floor of the transport vehicle such as a railroad car or a truck. The Hansen A-frame must be secured to the floor prior to loading. Once unloaded, the A-frame may be released from the floor and folded from side to side to a smaller configuration in an accordion-like fashion. The Hansen A-frame may not be transported when loaded, as it is secured to the floor before loading. It is rather complex, and would require several individuals to accomplish its folding and unfolding.
Another A-frame structure is revealed in U.S. Pat. No. 5,085,329 issued to Crowell et al. The A-frame disclosed in Crowell is intended for the temporary storage of 4 foot by 8 foot sheet construction materials such as plywood, paneling or particle board which, of course, are substantially lighter in weight than glass sheets. In addition, the Crowell A-frame is disassembled for transportation and is not transportable when loaded.
U.S. Pat. No. 5,411,360 issued to Hilliker et al., discloses a collapsible, stackable A-frame rack intended for transporting large glass sheets. The Hilliker A-frame includes three A-frame stanchions which may be removed from the A-frame base after the A-frame is unloaded. The A-frame stanchions may then be nested on top of the base in a horizontal orientation which allows for the A-frame assembly to be stacked for return transport. An additional aspect of the Hilliker A-frame structure is that the structure is adapted to be transported on a dolly jack which, when positioned beneath the A-frame rack, may lift the A-frame rack. The A-Frame rack and dolly may then be transported by towing. The structure of the Hilliker device causes the lower edges of the glass sheets to be carried a substantial height above the floor. This requires that glass sheets be lifted to a relatively great height for loading and unloading upon the Hilliker A-frame and limits the size of panes that can be loaded under a given ceiling height. Loading of glass from the end of a float glass production line accordingly would be relatively difficult. The collapsed Hilliker A-frame rack includes a multitude of loose parts that must be kept together for return transit and which may be prone to loss.
Another aspect of transporting glass sheets is that of securing the glass during transport to prevent the glass panes from shifting with respect to each other with consequent breakage. A variety of approaches have been taken including the use of wedges, brackets, and straps to restrain the glass sheets during transit.
Strapping is probably the most commonly employed approach to securing glass sheets during transit. Strapping is typically stretched over the material to be restrained and then tensioned by a ratcheting mechanism. A number of currently existing strapping schemes exist which may allow adjustment of the location of one end of the strap by sliding it along a channel. For example, U.S. Pat. No. 5,448,805 (Allen et al.), discloses a strapping mechanism for use with a roof top carrier. One end of the strapping mechanism may be slid along a channel to various locations to compensate for the width of the load.
Another strapping mechanism is disclosed in U.S. Pat. No. 4,278,171 (Millhoan). This patent discloses a sliding strap retainer and compression block. The compression block includes a pair of spaced plates that are mountable at the base of an A-frame rack. The plates each have a pair of holes for selectively positioning the block on the base by aligning the holes of each plate with a hole in each base of the frame while biasing the block against the sheets of glass. Thereafter, a strap is secured at one end to the block and at the other end to the top of the A-frame. The strap is tightened drawing the block toward the sheets of glass. The Millhoan device requires the manual positioning of the compression block on the A-frame in order to secure the sheets of glass. Further, the Millhoan device does not allow the straps retaining the glass sheets to lie flat against the surface of the sheet of glass increasing stress at the edges of the glass sheet.
It would be preferable to have an A-frame rack for storing and transporting glass sheets which has the lowest possible center of gravity and a low lift height for loading and unloading. In addition, it would be preferable that such an A-frame structure be readily transportable with a low dolly jack apparatus. Further, it would be desirable for an A-frame structure to be reduceable to a compact empty shipping size by one worker, preferably without the need for tools. Further, it would be helpful if the compacted A-frames were stackable for return shipping. Moreover, it would be a benefit if the A-frame structure would have a self-tightening, self-adjusting restraining mechanism for securing the glass sheets in place for shipping. Finally, it would be desirable to provide an A-frame rack useful in transporting glass sheets from a glass float line to a subsequent manufacturing line with requiring an intermediate unloading step.
The present invention in large part solves the problems referred to above by providing a unitized, foldable transport rack for retaining and securing panels, such as sheets of glass. The transport rack of the present invention in its preferred embodiment has no loose parts and is foldable and unfoldable by a single individual. The foldable transport rack has a low center of gravity and a low lift height to ease loading and unloading and to maximize the size of glass sheets that can be transported. In addition, the foldable transport rack of the present invention is transportable by a low dollyjack and includes self-adjusting securing straps which urge the bottom of the carried objects against the A-frame assembly to provide for secure transportation of large objects, such as glass sheets.
The transport rack generally includes a base, a plurality of supports for supporting panel edges, at least one foldable A-frame, and optionally a securing assembly. In one embodiment, the base of the transport rack is supported by a plurality of legs including the supports, the latter being adapted to handle and retain the lower edges of glass sheets or other objects to be carried by the transport assembly. The legs engage a horizontal surface, commonly a concrete floor, upon which the transporting rack rests. The supports are configured to be as low as possible to the ground so as to provide for a minimal lift height for loading and unloading. More specifically, the low arrangement of the supports provides for the loading of the transport rack directly from an automated manufacturing assembly. Furthermore, this arrangement also maximizes the size of objects that can be carried and maintains the lowest possible center of gravity. It is noted that the upper surface of the supports may be optionally cushioned with appropriate resilient material to provide additional protection to and retention of the materials loaded upon the transport racks.
The base of the transport rack may also define a corridor into which a low dolly jack may be received. The low dolly includes a plurality of lifting jacks by which the transport rack may be lifted from the ground, supported on the dolly and towed by an appropriate vehicle such as a forklift or tractor. The base also supports at least one and preferably three foldable A-frames. The A-frames are configured to be foldable parallel to the base for compact storage when it is desired to transport the empty transport rack back to its point of origin for reuse.
In one embodiment of the present invention, the outer two A-frames may be configured to be hinged near the base so that the outer two A-frames fold toward the center of the transport rack and lay one on top of the other. If a third or further A-frame is employed, it may be configured to fold at multiple locations, such as two locations, one near the base and the other in the mid-section of the A-frame. This allows the interior A-frame or A-frames to fold such that the outer A-frames may fold on top of the interior A-frames without interfering with one another and still allow all A-frame components to remain within and proximate to the base.
Also in an embodiment of the invention, the A-frames, when standing upright, are secured by a series of locking blocks which are on the opposite side of the frame from an associated hinge. The locking blocks each define a bore through which a pin may be passed to lock the A-frame in an upright position. The locking pins in such an embodiment may be secured to the transport rack by a lanyard or may be integrally attached to one of the locking blocks such that the pin is spring biased and may be latched in an open position or biased by the spring to a position passing through the bores to lock the hinged joint in an upright position.
Embodiments of the transport rack further comprise a securing mechanism that includes straps, which pass from the top of each A-frame down over the load to be secured and are then secured at the support. The support includes a traveler to which the straps may be secured. The traveler slides in a slot. The slot is ramped upwardly and inwardly toward each A-frame so that applying tension to the strap tends to urge the strap inwardly toward the objects to be secured. The tensioning of the strap can be accomplished with a conventional ratcheting buckle or other appropriate means.
In yet another embodiment, the invention provides a method for storing and transporting panel-like objects such as glass sheets while avoiding the problems encountered in repeatedly loading and unloading stacks of panels from a rack. A rack is provided, comprising a base, at least one support proximate a floor on which the rack rests, the support extending outwardly away from the base, and at least one A-frame member hingedly attached to the base, the A-frame member being foldable from a generally upright orientation to a generally horizontal orientation while remaining attached to the base. At a first location, panel-like objects are loaded one at a time onto the support, the objects being positioned parallel to each other to form a stack that leans against said A-frame member. Without removing the panels in stack form from the rack, the rack is transported to one or more different locations ending at a final location, and at that location, the panels are unloaded one at a time from the rack. In the case of glass sheets, the first location may be adjacent a float glass manufacturing line to receive glass sheets one at a time from the float glass line. The final location may be at a glass sheet coating line, where the glass sheets are unloaded one at a time to undergo a coating process.